Tabletop steam sterilizer

ABSTRACT

A tabletop steam sterilizer having an automatic refill means for introducing a measured amount of water into the sterilizer at the start of each sterilizing cycle. The refill means include a water container having a known volume, and the container is completely emptied into the sterilizer at the start of each cycle and refilled at the end of the cycle partly with condensed steam and partly with water from a separate reservoir. In one embodiment, the container is a plunger chamber wherein a solenoid operated plunger is used to inject water into the sterilizing chamber. AT the end of the sterilizing cycle, steam exhausts through the plunger chamber into a water reservoir. The pressure of steam in the plunger chamber forces the plunger back in a return stroke and heats the chamber. Subsequent cooling of the plunger chamber creates a partial vacuum which draws water back into the plunger chamber from the reservoir to fill the chamber for the next cycle of operation. In another embodiment, the container gravity feeds into the sterilizing chamber. At the end of the sterilizing cycle, steam is exhausted through an ejector having its outlet in the container and its suction let in a water reservoir, so that water is pulled from the reservoir to condense the steam. This fills the container to overflowing so that the container is filled for the next cycle, the overflow being directed to the reservoir.

United States Patent ()1 "rice 3,834,872 Patented Sept. 10, 1974 3,834,872 TABLETOP STEAM STERILIZER Larry James Joslyn, Walworth, N.Y., assignor to Sybron Corporation, Rochester, N.Y. Filed July 3, 1972, Ser. No. 268,747 Int. Cl. A61] 3/00, 3/02 US. Cl. 21-94 3 Claims ABSTRACT OF THE DISCLOSURE A tabletop steam sterilizer having an automatic refill means for introducing a measured amount of water into the sterilizer at the start of each sterilizing cycle. The refill means include a water container having a known volume, and the container is completely emptied into the sterilizer at the start of each cycle and refilled at the end of the cycle partly with condensed steam and partly with water from a separate reservoir.

In one embodiment, the container is a plunger chamber wherein a solenoid operated plunger is used to inject water into the sterilizing chamber. At the end of the sterilizing cycle, steam exhausts through the plunger chamber into a water reservoir. The pressure of steam in the plunger chamber forces the plunger back in a return stroke and heats the chamber. Subsequent cooling of the plunger chamber creates a partial vacuum which draws water back into the plunger chamber from the reservoir to fill the chamber for the next cycle of operation.

In another embodiment, the container gravity feeds into the sterilizing chamber. At the end of the sterilizing cycle, steam is exhausted through an ejector having its outlet in the container and its suction leg in a water reservoir, so that water is pulled from the reservoir to condense the steam. This fills the container to overflowing so that the container is filled for the next cycle, the overflow being directed to the reservoir.

BACKGROUND OF THE INVENTION The present invention relates to tabletop steam sterilizers and more particularly to such a sterilizer having automatic refill capabilities, wherein a measured amount of water is introduced into the sterilizer for each cycle of operation.

Tabletop steam sterilizers are usually self-contained, i.e. they have a water reservoir to eliminate the need for external plumbing connections. Introduction of water into the sterilizing chamber is accomplished simply by manually opening a valve to permit water to drain by gravity from the reservoir and into the chamber. The valve is manually turned off when the operator observes the desired level of water in the chamber. The sterilizing cycle is then started by turning on a heater in the sterilizing chamber to convert the water to steam. At the end of the sterilizing cycle, steam is vented through a condenser coil in the reservoir to permit recycling of the water.

In the present invention, the cycle of operation is made completely automatic by providing means for introducing preselected amounts of water into the sterilizing chamber at the start of each cycle, the means being refilled automatically from the reservoir at the end of each cycle.

SUMMARY OF THE INVENTION One embodiment of the present invention may be characterized by a measuring cylinder in the plumbing between the reservoir and sterilizing chamber and a solenoid operated plunger in the cylinder. With the cylinder filled with water from the reservoir, starting the sterilizing cycle activates the solenoid. This causes the plunger to inject the water in the cylinder through valve means and into the sterilizing chamber, where a heater converts the water to steam. At the end of the sterilizing cycle, any suitable temperature and/or pressure sensor operates the valve means so as to exhaust the steam into the reservoir, at least part of the steam first passing through the measuring cylinder. The steam in the measuring cylinder forces the plunger back in a return stroke and heats the cylinder. Subsequent cooling of the cylinder creates a partial vacuum to draw water from the reservoir back into the cylinder for the next cycle of operation.

Another embodiment of the invention is characterized by having a water container of known volume arranged for gravity flow to the sterilizing chamber; means for completely emptying the contents of the container into the sterilizing chamber at the start of each cycle; a water reservoir; and means drawing water from the reservoir to mix with and condense steam vented from the sterilizing chamber at the end of the cycle. Water drawn from the reservoir and condensed steam are discharged directly into the container filling the container to overflowing thereby providing a measured amount of water in the container for the next cycle of operation, the overflow being directed back to the reservoir.

DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood upon consideration of the following detailed description thereof, when taken in connection. with the accompanying drawings in which:

FIG. 1 is a schematic representation of the sterilizer of the present invention; and

FIG. 2 is a view similar to FIG. 1, showing another embodiment of the invention.

DETAILED DESCRIPTION Referring to the drawings, FIG. 1 shows the tabletop sterilizer of the present invention generally indicated at 10. The sterilizer includes a sterilizing chamber 12 having a load/unload opening which may be closed by any suitable door member 14. Within the sterilizing chamber is an electric heating element 16. There may be various shelves or holding means (not shown) within the sterilizing chamber for receiving the articles to be steam sterilized. The sterilizer chamber is highly insulated, a portion of which is shown at 18, so that as much heat as possible is retained by the sterilizing chamber.

Sterilizer 10 also includes a water reservoir 20 which communicates through a pipe 22 with a cylinder 24. One end of pipe 22 forms a condenser coil 26 within the reservoir. The pipe itself contains a venting orifice 28 for purposes set out hereinbelow. Connecting cylinder 24 to the bottom of sterilizing chamber 12 is a pipe 30 which has two branch passages 30A and B, the flow through these branch passages being controlled by a solenoid valve 32 and check valves 34A and 34B. Pipe 30 communicates with the bottom of sterilizing chamber 12 through a sump 36.

In cylinder 24 is a plunger 38. The plunger is operated by a solenoid 40 outside of the cylinder. For purposes of adjusting the stroke of the plunger, the plunger has a threaded stem 42 and an adjustable stop 44.

The controls for the sterilizer include a start button and switch 46, and a sterilizing chamber pressure/temperature sensor and switch 48. The start button and switch 46 controls the operation of solenoid 40 and heater 16 through primary circuit portions 50 and 52 respectively. Temperature sensor switch 48 controls the operation of valve solenoid 32 through a secondary circuit portion 54.

Operation of the sterilizer It) simply requires that reservoir 20 be kept filled. This can be done periodically, say on a day to day basis, or perhaps at less frequent intervals. Chamber 24 is filled, say by manually moving the plunger to the position shown in FIG. 1 or by putting water directly into the sterilizing chamber 12 and running a dummy load. Thereafter plunger chamber 24 will be automatically refilled at the end of each sterilizing cycle, as set out hereinbelow. Assuming the plunger chamber is initially filled with Water, the operation will be described as beginning when articles to be sterilized are placed in sterilizing chamber 12 and door member 14 sealed.

To start the sterilizing cycle, push button switch 46 is closed. This energizes solenoid valve 32 to move the valve to the position shown in dotted line. Plunger solenoid 4.0 is also activated, which causes the piston 38 to move to the left, as viewed in FIG. 1. In this manner, the contents of cylinder 24 are injected through pipe 30, check valve 34A, branch pipe 30A and sump 36 into the sterilizing chamber. It should be appreciated that closing push button switch 46 also energizes the heating element 16. As the water in the sterilizing chamber is turned to steam, air in the chamber is displaced upwardly and is vented through a bleed orifice and air trap valve 56 at the top of the sterilizing chamber. As the steam pressure is built up in sterilizing chamber 12, steam is prevented from venting through pipe 30 on the one hand by check valve 34A and on the other hand by the position as shown in dotted line of solenoid valve 32.

The length of the sterilizing cycle in the present invention is determined by the saturated steam temperature within sterilizing chamber 12. However, it should be appreciated that any suitable time or pressure cycle may be used. In any event, when the saturated steam temperature increases to the desired level which is an indication that sterilization has been completed, temperature switch 48 is actuated. This opens circuit portion 54 to deenergize solenoid valve 32, allowing the valve to return to the position shown in solid lines in FIG. 1. This allows the steam to vent through sump 36, piping 30, check valve 34B, cylinder 24, bled orifice 28, piping 22 and through condenser 26 back into the reservoir. As the steam leaves sterilizing chamber 12, a reduction in pressure together with the retained heat in the sterilizer should cause the vaporization of any condensed moisture in the sterilizer.

The actuation of temperature sensor 48 also opens circuit portion 50 to deenergize solenoid 42. With the solenoid deenergized, the steam entering cylinder 24 pushes piston 38 to the right, as viewed in FIG. 1, in a return stroke. The passage of stream through piping 22 is restricted by bleed orifice 28 so that there will be an accumulation of saturated steam in cylinder 24.. The steam accumulating in the cylinder not only moves the piston in a return stroke, but also heats the cylinder.

When all of the steam has been exhausted into the reservoir, cylinder 24 will cool, creating a slight vacuum which will draw water back into the cylinder through piping 22 and bleed orifice 28. Since cylinder 24 had contained saturated steam, the condensing of this steam together with the water being drawn into the cylinder by vacuum should completely fill the cylinder with water. In this manner, the cylinder is automatically refilled in preparation for the next cycle of operation.

If it is found necessary to cool the reservoir 20, any suitable means, such as a fan 58 can be provided for this purpose. The operation of the fan can be controlled by any suitable means (not shown), such as temperature sensor responsive to the reservoir temperature, or the fan may be connected to circuit portion 50, so that it runs continuously during the sterilizing cycle.

If desired, the venting can be done manually as in an abort situation simply by providing means for opening the push button switch 46. In an abort situation, it is anticipated that the abort would occur before all of the injected water has turned to steam. In this case, the water accumulating on the bottom of the sterilizing chamber 12 and in sump 36 would be forced out by pressure in the sterilizing chamber.

Referring now to FIG. 2, the sterilizer shown includes a measuring container 60 having a known volume. Ad-

jacent container 60 is a water reservoir and overflow tank 64, the container and tank being separated by a wall or weir member 66. It should be appreciated that the container and tank need not be incorporated into a single vessel as shown, and that if the container and tank are spaced apart, other means may be provided to conduct the overflow from the container to the reservoir/ overflow tank.

4 Container 60 is located above the sump 68 of a sterilizing chamber, a portion of the sterilizing chamber being shown at 62. A pipe 70 connects the container to the sump for this purpose.

A second pipe 72 is connected to and communicates with pipe 70 and the inlet of an ejector 74. Ejector 74 has its suction leg 76 extending down into reservoir/ overflow tank 64. The outlet 78 of the ejector is arranged to discharge into container 60.

Completing the components of the embodiment shown in FIG. 2 is a three-way solenoid valve 80 controlling the flow through pipes 70 and 72, and a check valve 82 located in pipe 70 for purposes set out hereinbelow.

The construction and operation of the embodiment shown in FIG. 2 is simpler than the embodiment shown in FIG. 1, in that the plunger has been eliminated and gravity alone delivers water from the container into the sterilizing chamber. In operation, then, container 60 initially must be filled to overflowing. Since the entire contents of container 60 are drained into the sterilizing chamber at the start of each cycle, filling the container to overflowing ensures that the same amount of water is introduced into the sterilizer for each cycle. It should be noted that the overflow into reservoir/ overflow tank 64 should be suflicient to cover the inlet of suction 76 and, preferably, should substantially fill this tank.

After the articles to be sterilized are located within the sterilizing chamber 62, any suitable means such as a push button (not shown) may be operated to initiate the cycle. When the cycle is started, solenoid valve 84) is moved from the position shown in solid line in FIG. 2 to the position shown in dotted line. This permits all of the water in container 60 to drain through pipe 70 into the sump and sterilizing chamber. A heater in the chamber then converts the water to steam. As pressure builds up in the sterilizing chamber, any flow back through pipe 70 into the container is prevented by check valve 82 and the position of solenoid valve 80. At the end of the sterilizing cycle, as determined by any appropriate time, temperature, and/or pressure indicator (not shown), solenoid valve 80 is operated and moved to the position shown in solid line in (FIG. 2. With pipe 72 now open, steam is directed from the sterilizing chamber through a portion of pipe 70, pipe 72 and through ejector 74. The passage of steam through the ejector draws water from reservoir/overflow tank 64 through suction 76. The water is mixed with and acts to condense the steam, so that only water is discharged through outlet 78 into container 60.

Only a little of the venting steam is lost, so that substantially all of the steam is condensed and returned to container 60. This, plus the amount of water drawn from reservoir/overflow tank 64, will result in an overfilling of the container, the excess water flowing over wall 66 back into tank 64.. Thus, at the end of the sterilizing cycle, container 60 is automatically refilled to provide a measured amount of water for the next sterilizing cycle.

Tabletop steam sterilizers are usually designed so that the same amount of water will be used in each sterilizing cycle. Accordingly, reservoir 60 can be designed to hold the optimum amount of water and there should be no need to provide means for varying the volume of the measuring container 60. However, it is within the skill of the art to provide the container with an adjustable volume, say by having means to increase or decrease the height of wall 66, or by putting blocks in the container to reduce its volume.

Thus, it should be appeciated that the present invention provides a tabletop steam sterilizer having means for automatically refilling the sterilizing chamber with a measured amount of water at the beginning of each sterilizing cycle. While preferred embodiments of the invention have been described, it should be appreciated that various modifications are within the skill of the art. For example, all of the separate components shown in FIGS. 1 and 2 are preferably incorporated into a single cabinet or housing (not shown). In addition, the piping 22 and bleed orifice 28, as shown in FIG. 1, do not have to communicate directly with the cylinder 24. Instead, pipe 22 and bleed orifice 28 may be connected directly to pipe 30, between the cylinder and solenoid valve 32. With this arrangement, only a portion of the steam venting from sterilizing chamber 12 would be introduced into cylinder 24 to move the plunger in a return stroke and heating the cylinder.

Having thus described the invention in detail, what is claimed as new is:

1. In a tabletop steam sterilizer including a sterilizing chamber adapted to receive goods to be sterilized by steam and pressure, heater means for converting water in the sterilizing chamber to steam, a water reservoir separate from the chamber and piping communicating with and extending between the reservoir and sterilizing chamber, the improvement comprising means for injecting a measured amount of water into the chamber, comprising:

(a) a plunger chamber in said piping intermediate said reservoir and sterilizing chamber, said plunger chamber dividing said piping into two portions and communicating with each portion;

(b) a piston in said plunger chamber;

(c) means for driving said piston in a single, pumping stroke wherein substantially all the water in said plunger chamber is injected into said sterilizing chamber;

(d) valve means in the portion of piping between said plunger chamber and sterilizing chamber;

(e) control means operating said piston drive means and said valve means at the start of a sterilizing cycle to permit the injection of water in said plunger chamber into said sterilizing chamber, said control means thereafter, at the end of the sterilizing cycle, operating said valve means to permit at least a portion of the steam in said sterilizing chamber to vent into said plunger for driving said piston in a return stroke; and

(f) said steam in said plunger chamber thereafter condensing, whereby a partial vacuum is created in said plunger chamber for drawing water from said reservoir through said piping and into said plunger chamber to refill the same.

2. In a tabletop steam sterilizer having a sterilizing chamber adapted to receive goods to be steam sterilized, a water reservoir, and heater means to convert Water in the sterilizing chamber to steam, the improvement comprising fill means to deliver automatically a measured quantity of water from the reservoir to the sterilizing chamber comprising:

(a) a pump chamber for water, said pump chamber having a measured, known volume;

(b) a pipe extending between and communicating with said pump chamber and sterilizing chamber, and including valve means therein, said valve means permitting communication between said pump chamber and sterilizing chamber at the start of a sterilizing cycle;

(c) a plunger operable in said pump chamber;

(d) means driving said plunger in a pumping stroke for injecting substantially all of the water in said pump chamber into said sterilizing chamber;

(e) means including a valved conduit extending between and communicating with said pump and sterilizing chambers and conduit means in fluid flow communication with said pump chamber and reservoir for venting said sterilizing chamber through said pump chamber and into said reservoir, the pressure of steam venting from said sterilizing chamber and into said reservoir through said pump chamber causing said plunger to move in a return stroke; and

(f) refill means conducting water from said reservoir to said pump chamber at the end of the sterilizing cycle for substantially completely filling said pump chamber.

3. A tabletop sterilizer as set forth in claim 2 wherein said conduit means has an orifice therein, wherein the refill of said plunger chamber is accomplished by condensing the steam therein to create a partial vacuum for drawing water into said plunger chamber through said conduit means and orifice.

References Cited UNITED STATES PATENTS 3,481,692 12/1969 Linder 2194 3,065,509 11/1962 Vischer 21-94 2,592,884 4/1952 Fox et al. 21-99 3,717,434 2/1973 Black 21--94 BARRY S. RICHMAN, Primary Examiner D. LOVERCHECK, Assistant Examiner US. Cl. X.R. 

